We had a chicken that had a HUGE bite from a dog (we think), from her shoulder to her saddle area, about 5-6 inches in diameter. Her bite got infected, and we injected Penicillin G into her breast muscle with a .22 gauge syringe needle every other day for 4-5 days, and dressed it with antibiotic ointment. Your case doesn't look super severe, and if my chicken was able to recover from that bite, yours will be okay. I agree with Aapomp831 that you don't really need anything other than antibiotic ointment at the moment. If it gets infected, I would do what we did for my hen. However, I cannot stress enough that isolation is SO important!! Chickens naturally want to weed out the weakest flock member(s) and will try to kill injured chickens to keep predators from being attracted to the group. We had a chicken sneak into the injured chicken's coop as her wound was beginning to heal and pecked it right open again! She survived, but please make sure that no other chickens can get into her space!